Natural gemstones and diamonds are rare and require skill and tedious processing efforts to draw out the full beauty from the rough stone. Various different shapes of polished gemstones may be obtained from the rough stone; thus that the cut, which utilize most of the stone in terms of weight, shape and clarity, is the most profitable one. Thus, in order to realize the full potential and maximize market value thereof, it is desirable to determine in advance the optimal finished gem, which can be cut from the untreated stone.
In automated gemstone imaging systems known in the art, the scanned gemstone is maneuvered to a 360 degrees circle by means of a rotating gemstone holder. The image provided by those techniques are obtained separately and only one half of the gemstone is usually photographed at one session. The gemstone is photographed approximately at 5-degrees intervals, resulting in about 36 to 90 images for both halves of a gemstone, a relatively long procedure taking up to 30 seconds. The images are used to create a three dimensional picture of the gemstone. The system works by use of sequential repeat commands such as (1) take a picture; (2) rotate 5 degrees; and (3) stop; and by repeating these commands until the gemstone has rotated 180 degrees.
Moreover, a number of computerized scanning systems have been adapted to examine gemstones and diamonds and to compare the shape of the stone with a variety of predetermined shapes in order to establish the best fit. In one type of scanning system, the stone is lit from the rear, providing a silhouette thereof, which is analyzed by the computer and compared with a number of silhouettes of finished stones. In a second type such as that disclosed in U.S. Pat. No. 4,417,564, the stone is scanned perpendicular to the axis, so as to permit the computer to provide a three-dimensional image of the stone.
Both types of scanning systems discussed above may be advantageous in detecting protrusions but useless or ineffective in case of reentrants or recesses in the stone, which remain invisible; this may result in incorrect decisions regarding the proper working of the stones.
In a third type of system, such as that described in IL Pat. 66292, a thin beam of light is projected onto the stone and moved relative to it. The point where the beam strikes the stone as viewed in a direction different from that from which the beam is projected. However, this method may suffer from inaccuracies in the reentrants measurements.
U.S. Pat. No. 6,567,156 discloses a fourth type of examining method comprising coating the gemstone with a removable diffusing coating and determining the silhouette of the gemstone in three dimensions. The method further includes structured light triangulation performed by using laser light to obtain an image of the surface of the gemstone.
Gemstone clarity is a measure of a gemstone's lack of internal flaws and impurities. A gemstone that is virtually free of interior or exterior inclusions is of the highest quality, for nothing interferes with the passage of light through the gemstone. As inclusions gravely degrade the finished stone's value, it is desirable to take them into account when optimizing the cut. However in many cases these inclusions are not visible or locatable until late stages of the polishing process, and thus cannot be avoided in advanced refining stages.
A manual method for determining inner inclusions is only partially provided by means of carving a small picking hole or window into the stone and probing through it, using an optical fiber or a stent, in the search for such inclusions. Clearly this method cannot map all inclusions potentially residing in the stone and further risks damaging the stone, in part or in whole
In WO 02/46725 to Sivovlenko et al., a method and apparatus for locating inclusions in a diamond is disclosed, wherein said diamond is fixed on a holder and observed under a predetermined angle to obtain an image. A second measurement is carried out to obtain data to be calculated in a computer, either by a depth measurement, or by changing the direction of observation, in order to localize the inclusion with respect to the outer surface of said diamond.
It is thus acknowledged that there is no reference in the prior art that the inner portion of the gemstone, comprising potential inclusions are detected or located in a non-destructive means prior to the gemstone processing stages.
A cost-effective method and system for three-dimensional mapping of both the outer and inner surfaces of a gemstone, useful for optimizing yield, thus meets a long felt need.